Test fixtures for the pressure testing of plumbing drainage or vent pipes and stacks are well known in the art. As required by building codes in the installation of plumbing systems, particularly waste or vent pipes in buildings, it is necessary to pressure test the pipes for leaks. The present method is to cut the pipe an temporarily insert a complicated test valve arrangement (called a "wye" having a "double test plug") which blocks the pipe. A head of water is then applied upstream of the valve, and the drainage line is checked for leaks. After the test, the test valve must be removed and replaced with a permanent coupling. This procedure is troublesome in that the test valves are expensive and tend to wear out frequently, and the process is labor intensive by virtue of the necessary cut, insertion, removal, and permanent coupling installation steps.
Prior art devices which address the temporary closure of pipe systems include U.S. Pat. No. 2,645,244 which shows a close-off device for pipe lines which is useful in cleaning the pipe system. A disc-like sealing device is temporarily inserted in the line. The sealing device has grooves or channels which allow impurities to be purged from the system. U.S. Pat. No. 4,194,721 illustrates a plumbing test fitting for waste or vent pipes. The fitting has a closure plate adapted to be slidably fitted between a pair of spaced adjacent ends of a pair of pipes, the joint being sealed by a detachable sealing clamp which also bears against the periphery of the closure plate. A sliding valve element having an operating stem which extends outwards between the pipes and through the sealing clamp can be operated to open or close a passage in the closure plate so as to enable the pipe to be closed for testing and thereafter opened to permit testing fluid to escape down the pipes. The device must be removed after the completion of testing and replaced with a permanent coupling. U.S. Pat. No. 4,429,568 describes a closure plug assembly for pressure testing liquid drain and vent plumbing pipe systems. The device includes a T or Y test section with a test opening which compresses a cap subassembly, sealing means for releasably securing the cap sub-assembly across the test opening, and a plug such as an inflatable bulb or plate removably insertable in the plumbing system.